SANTA CLARA — Of the 90 players who reported to 49ers training camp Wednesday, 23 are not under contract for next season, not to mention a handful of young stars who are poised for contract extensions.

"Anybody that says it's not a concern, they're probably lying," Whitner said of heading into a contract year. "It's always a concern, especially when you're in a business that's so physical. You never know what's going to happen on a football field.

"But I'm not in a position to make anybody do anything. All I can do is work hard every day, help lead the secondary, help continue to make sure we're one of the top defenses in the NFL, and everything else will fall into place."

Among the promising players who are under contract in 2014 but could warrant an extension before then are quarterback Colin Kaepernick, linebacker Aldon Smith, guard Mike Iupati and wide receiver Michael Crabtree.

Cornerback Carlos Rogers is signed through 2015, but his $5.5 million base salary this season has led to media speculation he could be too expensive to keep among a competitive, crowded unit.

"I've heard that but I can't control it," Rogers said. "They'll make their decision. ... My goal is to play here for this team."